Reactions of ethanol and formate radicals with ribonuclease A and bovine serum albumin in radiolysis.

Aqueous solutions of ribonuclease and bovine serum albumin were irradiated under N2O in the presence of ethanol or formate, which was partly 14C-labelled. The amount of bound ethanol and formate was measured after separation by gel filtration. Reactions of ethanol and formate radicals with proteins lead to covalent crosslinks between the organic solutes and the proteins as well as between the protein molecules. The amount of bound ethanol or formate depends on the structure of the protein and its degree of denaturation. Based on these results and known pulse radiolysis data a mechanism for the reaction of the organic radicals with proteins is proposed. Radiation-induced crosslinking of organic solutes to proteins can be used for studying protein structure in solution.